Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 110441
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
1041 PM CST Sat Feb 10 2018

.UPDATE...
Issued at 1041 PM CST Sat Feb 10 2018

The winter weather advisory has been cancelled for our western
zones where snow has ended this evening.

&&

.SHORT TERM...(This evening through Sunday night)
Issued at 415 PM CST Sat Feb 10 2018

By FAR the main focus of these next 36 hours comes right away
during these first 12 hours, as we see ONE LAST round of generally
1-4" of snow before the weather pattern finally quiets-down for a
while, with the overall-highest amounts expected to focus within
1 county either side of the Nebraska-Kansas border, and the
lowest amounts expected in our north mainly north of Neb Highway
92. In other words, most of the areas that saw little to no snow
last night should pick up the brunt of the snow this time around
(and vice versa). On a positive note, and unlike last night, winds
will be much less of a factor, with sustained speeds largely at-
or-below 10 MPH. Despite these light winds, a secondary concern
will be another round of near-Advisory wind chill values late
tonight into Sunday morning, but unless things trend colder we
should be "safe" from any headlines this time around.

Taking a look at the current/recent weather scene as of 330 PM...
Overall, today has turned out largely as expected. Following a
brief break in snow across our entire area coverage area (CWA)
late last night into this morning, areas of mainly light snow have
already broken out this afternoon especially in several of our
southwestern counties, steadily expanding eastward with time. In
the mid-upper levels, a broad trough is in the process of
translating through the central CONUS, with our expanding snow
band being driven by forcing associated with an upper level jet
streak and especially mid-level convergence/frontogenesis
particularly noted around the 700 millibar level. At the surface,
a roughly 1026 millibar high pressure is centered in over
northeast Nebraska, with a much-weaker pressure gradient than
yesterday only promoting north winds around 10 MPH for most of the
CWA. Although today was already expected to be very cold, if
anything, high temps will fall slightly short of expectations from
night shift, with most areas only topping out 8-12.

Now looking ahead forecast-wise through these next 36 hours, with
particular focus on these first 12...

Late this afternoon-tonight:
Starting with a quick review of changes to the Winter Weather
Advisory outlined in an earlier update discussion: Since this
morning it was expanded 1 row of counties north to include the
Highway 6 corridor, and the official Advisory end times were pared
back to Midnight (in the west) and 3 AM (in the central/east). For
most of the CWA (especially outside the far southwest where it is
already snowing steadily), the majority of snow will fall between
6PM-Midnight. Overall, most models (including larger scale and
higher-res) are in reasonably-good agreement on how this plays
out, which bolsters confidence in at least having the general snow
accumulation scenario fairly well covered. See our website/social
media posts for the more detailed graphical depictions, but we are
calling for a range from 1" or less near/north of Neb Hwy 92, 1-2"
within the I-80 corridor, and 2-4" in most areas southward from
there covered by the Advisory. Within the Advisory however, the
overall highest amounts around 4" (perhaps locally higher?) are
expected to concentrate within 1 county either side of the NE-KS
border, with lesser amounts in both the northern part of the
Highway 6 counties, and also the southern parts of the
Rooks/Osborne/Mitchell counties in KS. Probably the two biggest
question marks at this time are: 1) Are we high enough with the
max amounts near the state line in the heaviest banding?...2)
Might be need to consider including the I-80 corridor in the
Advisory if 2+" potential creeps northward any farther than it
already has? These concerns/possible changes will be addressed by
the incoming evening shift, but again, the "big picture" of this
snow event seems to be pretty well in hand at this time.

As the responsible mid-upper level wave and associated
frontogenetic forcing gradually departs our CWA to the east-
southeast after midnight, snow will steadily depart/end from
west-to-east as well, and unless things slow down, only perhaps
our far southeast zones should still have any accumulating snow
still ongoing post-midnight, and even then for only a short time.
As snow ends, expect a relatively robust clearing of skies as
well. Although surface winds late tonight will only average around
8 MPH or less from a westerly direction behind the departing
system, even these light winds could promote near-Advisory wind
chills as low as -10 to -15 degrees (locally worse?). As for
actual low temps, nudged down, and perhaps not enough, but most
areas are aimed very slightly sub-zero.

Sunday daytime:
FINALLY, a break from snow chances! Expect mostly sunny to mostly
sunny skies, with light westerly winds in the AM turning more
southerly in the afternoon, but with speeds largely only around 10
MPH or less. Despite plentiful sunshine and the west-southwesterly
wind component, our current/new cover will be a force to content
with regarding a big warm-up, and have nudged down highs 2-3
degrees from previous. Confidence isn`t the highest, but have a
range from mid-upper 20s in most Neb zones, with low 30s more
favored in our KS zones and also far western Neb zones (perhaps
mid 30s extreme south?).

Sunday night:
Dry weather should persist, although a frontal boundary will sag
southward toward the area as the night goes on, turning breezes
more easterly versus southerly. Low temps are expected to range
from near-zero northeast to around 8-10 far south/southwest. We
could have wind chill values again nearing -15, but are currently
expected to fall short of Advisory levels.

.LONG TERM...(Monday daytime through Saturday)
Issued at 415 PM CST Sat Feb 10 2018

General overview of this 6-day period:
With all the short term concerns, have spent less time than usual
diving into the details of this time frame. However, here are the
two main takeaways: 1) Although not truly "warm" by any means,
there are at least two "milder" days lurking in the forecast, and
nothing looks nearly as cold as yesterday-today have been. 2)
Precip-wise, there are some relatively small chances for snow
currently indicated for parts of the CWA for both Monday evening
and again Friday into Saturday, nothing at this time looks "major"
or overly-organized.

Temperature overview:
Lately, it seems like all we`ve been doing is lowering
temperatures as days get closer (primarily due to increasing snow
cover), and unfortunately that will probably be the case again
through at least mid-week. Starting with Monday, highs were
lowered 2-5 degrees from previous, but with a decent range from
only around 20 far north, to around 35 far south. A bit of a warm-
up is then anticipated Tuesday into Wednesday, with Tues mainly
30s north/40s south and then more widespread 40s north/50s south
for Wednesday (Valentine`s Day). However, although we should melt
some snow Wednesday, do not be surprised if readings trend down a
bit as it gets closer. For Thursday-Saturday, temperature
uncertainty starts to increase, but early indications suggest
mainly highs in the 30s for Thurs-Fri, with maybe (key word MAYBE)
a bit of a warm-up again Saturday with more of the area into the
low-mid 40s.

Precipitation overview:
Early in the week, Monday into Monday night bears watching for
some pesky light snow brushing parts of the CWA. For now, the
official forecast only has a small chance in northern zones Monday
evening, but will have to make sure other areas don`t at least
deserve a slight chance mention. Confidence in the precip-free
forecast is pretty high for Tuesday-Thursday. Then Thursday night
into Friday, we have some very low snow chances in Neb zones, but
this is more supported by the ECMWF than the GFS. Finally,
uncertainty grows even more for Friday night-Saturday morning:
While our official forecast advertises modest snow chances (albeit
less than "likely"), the latest deterministic runs of the
ECMWF/GFS are bone dry for these same periods.

&&

.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Sunday)
Issued at 510 PM CST Sat Feb 10 2018

Snow continues to work to the north and east this evening and snow
is already falling at both KEAR and KGRI. For the most part, snow
is expected to remain relatively light at the terminals with
accumulations averaging 1 to 2 inches of fluffy snow. The snowfall
will be the most widespread during the evening, before tapering
off around midnight or shortly thereafter. Winds are expected to
remain fairly light through the TAF period.


&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...Winter Weather Advisory until midnight CST tonight for NEZ073-
     083.

     Winter Weather Advisory until 3 AM CST Sunday for NEZ074>077-
     084>087.

KS...Winter Weather Advisory until midnight CST tonight for KSZ005-
     017.

     Winter Weather Advisory until 3 AM CST Sunday for KSZ006-007-018-
     019.

&&

$$

UPDATE...Fay
SHORT TERM...Pfannkuch
LONG TERM...Pfannkuch
AVIATION...Fay



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